Preparation and properties of cis-dialkylcobalt complexes, CoR 2(acac)(PR′ 3) 2

Abstract

Treatment of Co(acac) 3 and tertiary phosphine with AIR 2(OEt) in ether under nitrogen gives remarkably stable trivalent cobalt complexes, CoR 2(acac)(PR′ 3) 2 (R = Me, Et, n-Pr, iso-Bu, PR′ 3 = PEt 3, P(n-Bu) 3, PPhMe 2, PPh 2Me; acac = acetylacetonato). 1H, 31P and 13C NMR spectra of these complexes show that they have an octahedral configuration with two tertiary phosphine ligands in axial positions. Pyridine replaces one of the phosphine ligands to give a pyridinecoordinated complex, Co(CH 3) 2(acac)(PEt 3)(py), whereas a bidentate ligand 2,2′-bipyridine replaces both tertiary phosphines to yield the bipyridine-coordinated complexes, CoR 2(acac)(bipy). The isolated complexes readily react with carbon monoxide to yield the dialkyl ketone and a univalent carbonyl complex with an acetylacetonato ligand, Co(acac)(CO) 2(PR′ 3).